Multiple site communication systems which comprise a plurality of repeaters and transceivers that are distributed throughout a large geographic region are well known. Many multi-site systems use same-frequency simulcast, i.e., the same communication channel (or carrier frequency) is used by multiple sites throughout the region to simultaneously relay communications to subscriber communication units that are located throughout the multi-site system. This is an efficient frequency reuse technique when the subscribers are routinely located throughout the multi-site system.
The use of comparators, and their associated voting algorithms, within simulcast communication systems is known. In general, a comparator, operably coupled to a plurality of base stations or satellite receivers located in geographically diverse areas, attempts to select or construct a favorable representation of an audio signal given multiple sources of the signal (e.g., the base stations). This is accomplished by comparing the signals received from the signal sources and selecting, from amongst all of the signal sources, portions of the signal having the best signal quality. The selected portions are then reassembled to produce a favorable voted signal frame. The voted signal frame can then be retransmitted by a base station, thereby increasing the probability of good reception (i.e., intelligibly decoded audio) at the signal destination (e.g., a mobile communication device). The signal selected as the best by the comparator is typically distributed therefrom to the transceiver sites for simultaneous re-transmission.
More recently, digital simulcast radio communication systems have been developed. In such systems, digital information is formatted into information frames. Each information frame is made up of a plurality of information packets that are transported through the system infrastructure.
Current systems allow for a single voting session to occur in each comparator, i.e. each comparator operates on and is dedicated to a single radio channel. This does not provide a cost effective means for operating in multi-channel trunking systems, systems where each radio channel represents a single radio frequency or a single time division multiplex (TDM) slot, since a separate comparator is necessary to service each of the multiple radio channels. Also in the current scheme the radio receivers of a given channel have connectivity only to a single comparator which does not provide fault tolerance in the event that the comparator fails, since currently the entire radio channel becomes inoperable.
The trunking (dynamic assignment) of single channel capable comparators is known. This trunking scheme employs a digital circuit switch to reroute all the individual point to point connections between each comparator and each of multiple base station receivers for each radio channel.
Conventional comparator trunking techniques do not allow for multiple radio channels to be serviced from a single device. Consequently, at present there is no way to load share the voting services in the event that a failure occurred to one or multiple comparators.
In addition, because each comparator must be provided with the capability of interfacing with all available base sites, when a specific voting session involves only a subset of the available sites, the remainder of the processing capability in the comparator could not be used to process another session. Conventional comparators and their associated algorithms do not provide a connection mechanism by which multiple radio channels could be brought into a single voting device to enable the former.
Therefore, a need exists for a providing voting services on multiple radio channels simultaneously by a single device and which device can be dynamically assigned (trunked) to service any given radio channel, for example, on a packet by packet, call by call, or less frequent basis.